1. Field of the Invention
The present invention relates to a casting mold set that includes a core.
2. Description of Related Art
When a casting in a complex shape, particularly a casting that has a space inside (a die casting) is cast, in addition to a mold that defines an outer shape of the casting (appearance profile), a mold that defines the space inside of the casting is used. The mold that defines the outer shape of the casting typically includes a drag, a cope, and a cheek. Some mold sets define the shape of a cavity with only the drag and the cope, and some mold sets define the cavity with the cope, the drag, and plural cheeks. Herein, assembling the mold set to define an enclosed space of the cavity is referred to as “closing a mold.” The mold “set” herein means a group of molds that are necessary to define the cavity and includes a “core” that is described later. In addition, the term “casting” that is described herein is a general term of a product that is cast with a mold and includes castings that are made of not only cast iron but also other metals such as aluminum (aluminum die castings).
The mold that defines the interior space of the casting is called a core. In this specification, a part of the core (end) is referred to as a core print, and a part other than core prints is referred to as a casting shape forming part. The “core print” is a term that is used in casting engineers. The core print is a core end that does not contribute to the shape forming of the castings, and its upper and lower parts are held by the other parts. The core print is most commonly held by the cope and the drag, or the drag and the cheek. The “casting shape forming part” is a part of the core except for the core prints, namely, a part that contributes to the shape forming of the castings. In other words, a surface of the casting shape forming part corresponds to a cavity surface.
In the casting production such as aluminum die casting, the core is fabricated by baking a mixture of sand and resin. The resin serves as a binder to compact the sand. Such the mixture of the sand and the resin is also called resin coated sand.
The strength of the core that is made of the sand is not so high. Therefore, when the mold set is closed, if the core is strongly caught in the other mold, the shape of the core may be affected. Thus, a gap with a predetermined clearance is usually provided between the core and the other mold in a state where the mold set is closed.
The core that is made of the sand is lighter than molten metal in weight, and thus when the molten metal is poured into the cavity, the core floats by the gap with the clearance. A technique that prevents the core from floating is disclosed in Japanese Patent Application Publication No. 5-253663 (JP 5-253663 A), for example. The technique disclosed in JP 5-253663 A includes a slide rod that presses the core print against the drag from above after the mold set is closed.
However, if the core is pressed from above, a gap remains above the core. If the gap remains between the casting shape forming part and a mold that is located above the casting shape forming part of the core, the molten metal flows into the gap, and a so-called “burr” may be produced.